1. Field of the Invention
The invention relates to a power output device, a method for controlling the device, and a vehicle that is equipped with the device.
2. Description of the Related Art
Power output devices have been proposed in which an engine, a generator and a motor are controlled to output a required driving force to a drive shaft. In such devices, the depression amount of the accelerator pedal operated by the driver and the present vehicle speed are detected, and used to calculate the required driving force. An example of this type of device is described in Japanese Patent Application Publication No. JP-A 11-343891.
In the device described in JP-A 11-343891, the required driving force is set based on the depression amount of the accelerator pedal and the vehicle speed. However, as a result of setting the required driving force in this manner, there are some situations (described in more detail below) when the output driving force does not meet with the driver's request, or in other words, when the driver does not obtain the driving force he/she want as a result of depressing the accelerator pedal. More specifically, the driving force that a driver wishes to obtain when depressing the accelerator pedal varies depending on the speed at which the vehicle is moving. For example, when the vehicle is traveling at a low speed and the driver wants to accelerate forward quickly, he/she will wish to obtain a rapid increase in driving force by just depressing the accelerator pedal lightly. Alternatively, when the vehicle is traveling at a high speed and cruising, the driver will want to maintain the vehicle's speed with a stable driving force, without having to delicately and constantly adjust depression of the accelerator pedal. Furthermore, when the vehicle is traveling at a high speed and the driver wishes to pass a vehicle in front, he/she will want to obtain a rapid increase in driving force without having to depress the accelerator pedal forcefully beyond its present position. However, devices like that described in JP-A 11-343891 do not take into consideration the driver's request when setting the required driving force, and thus are not able to respond effectively in situations like those described above.